Air blowing but no heat. Just put new heater core?

 

Is your engine getting warm? Have flow through the heater core?

 

could have air in the lines. If you do you may need to burp the system
the valve might not be opening to let water into the core. it is on the fire wall.
your truck might be running cold, do you have a proper working thermostat? or a thermostat at all? although you would likly still get some heat.
your heat selector switch may be disconnected or broke in some way.
some other things too.

 

I just installed a new jasper motor. How do I "burp the system"?

 

1st generation heat only blows in defrost, and in heater setting. If you are trying to get heat out center or side vents it won't happen (mabe a little once interior is warm). Only floorboard, and windshield. Blower motor is above heater core, and if center vent is open air does not pass through heater core very well because center vents are on same side with blower motor. floor and defrost vents are the only ones on the opposite side of heater core.

Did your car have factory A/C? If so the outer dash vents are tubed into the center dash vent, but no heat will present itself from these locations only AC and outside air.

If truck was factory No AC the 2 outer dash vents are plumbed straight into outside cowl box. They have to be turned sideways to close them.

You can look at firewall on passenger side to determine ac or non ac'd truck as it will have 2 holes drilled for AC lines or not.

Hope this helps.

M

 

so big flapper on front of heater box should be closed, and outer dash vents should be turned sideways(closed) for the inside of truck to get warm.

 

burping system is bleeding air pockets out.
crack radiator cap (cold engine) don't get burned
park truck with nose pointed up a incline, nothing crazy just up hill.
open heater valve all the way
crank truck
remove radiator cap rest of the way
let thermostat open (water will start moving, thermostat be a hair under middle mark, water level should drop in radiator)
top off system while its running
close it up.

Should be burped.

M

 

Thank guys! Also the bottom lever for the heat and vents is stuck on deforst, "all the way to the left". I cant move lever to the right where it says "VENT". Guess the cables are stuck or hung-up some how.

 

you should be able to chase those controls down, they are on passenger side of heater box I believe if nothing else pop the cables loose at the heater box and flip the flaps yourself the way they need to be. That's what I did before I got new cables. Make sense?

 

Yup!.....

 

I have the cables/controls that fit your truck. I bought the setup from an 83 but needed the older style. I have fixed mine, but still have the newer controls, with cables.

 

msane99 you have a PM.

 

My 1980 quit blowing hot air. Found the heater core was stopped up.With the engine warm, grab the heater hoses to see if they are hot, if they are not warm, your heater core may be stopped up. I removed the heater hoses after clamping them off with a proper set of clamping pliers to avoid damaging the hoses, vise grips with duct tape on jaws will suffice in a pinch. Then connected an old garden hose with the end cut off to heater connection and blew the trash out of the core. Works like a charm now Oh, I also put a short piece of garden hose on the other heater connection to avoid spraying crap all under the hood. If no water flows at first, try swapping the garden hose to the other heater connection.

 

Ok so I just manually closed the bottom vent that's behind the bottom Gauges. Now I have heat defrosting the windshield now!!! Also heat coming out of the small vent holes on top of the dash pad. But I have just normal air coming from the front vents. How is it possible to have hot air from the top vent dash and normal air form the front vents? I must have some cables mixed up or I have to manually open/close the vent doors by hand.... At least I've found some heat!

 

hey Joe sorry I haven't gotten back to you. Been crazy, with Kids, football, band, birthdays, Halloween, ect .

alright the flap on bottom of box is the floor heat vents. if your dash was on the heat setting this would be the only flapper open on entire box. when set to defrost I think that all flappers are closed including one behind gauges. this forces air up the ducts on each side of heater box into the defrost vents on top of dash, and also to those 2 little round vents on top of dash (if so equipped). these are the ones on top of dash not facing driver but facing ceiling. these are for defrosting side windows and they T off of defrost ducts.

The middle vents above gauge cluster will NEVER blow hot air. neither will 2 round vents on each side of dash. these three are setup for fresh air, or recirculated air, but no air that blows through them ever goes through the heater core, therefore this air is never warmed before reaching the cab of the truck.

so:

Heater control valve on firewall open
Flapper on very bottom of heater box open
Flapper in middle of heater box closed
Flapper on outside air box under passenger dash closed
2 outer round vents turned sideways (closed)
fan on
=

Heat in floorboard and heat in defrost vents (these are the only places heat will ever come out)

I have an old rabbit that is ducted the same way. never heat out of the dash vents only floor and windscreen.

M

 

Thank you!

 

No problem bud! I haven't forgot that climate control either. right now I'm still trying to track down 2 of the cables.

 

msane99,
How do you get the heater control valve cable loose from the control lever inside the cab on a 1980 P/U? I can see a metal retainer holding the blue cable housing from under the dash, but don't see how to remove it. Do you have to remove the dash pad and remove the retainer from the top side? My contro lvalve stuck and it bent the cable. It will pull the valve open for heat, but won't push the control valve lever forward to shut heat off.

 

@mwisham

Hey I sent you an email. that retainer needs to be pinched on back side and it will let go. easiest is to remove plastic dash face. then controls on 80 are bolted down to dash frame. 8's or 10mm's undo those slide it out a bit and you will have good access/vantage point to see what's up.

M